Today's electronic kit such as mobiles, Smartphones, tablets, etc., are offering ever more functionalities, such as video, audio, GPS (Global Positioning System) positioning system, Internet and various connectivities, for example radio multi-systems with Wifi, Bluetooth, UMTS (Universal Mobile Telecommunication System), HSPA (High Speed Packet Access), LTE-Advanced network technology, which means that today the energy capacity of these onboard systems is under great strain. In the years ahead it is estimated that at least 70% of mobile communications will be transfers of video content. Conscious of these issues, the MPEG committee within the ISO has launched an initiative aimed at standardizing means allowing video decoders to minimize their energy consumption and thus to improve their duration of use. This standard is known by the name “Green Metadata”. Various solutions are known from the prior art and described in the ISO/IEC DIS 23001-11 standard of the “Green Metadata” standard.
To manage energy consumption in the best way, the Samsung company is proposing to modify the on-screen display of video and to reduce the screen supply voltage. Another procedure proposed by this company is dynamic control of the frequency which consists in anticipating and in adapting the computational power to the complexity of the video to be decoded.
The Thomson Video Network company is proposing an adaptive streaming procedure which consists in offering the decoder several versions of one and the same video on a DASH server, the abbreviation standing for Dynamic Adaptive streaming over http.
The Morphbius company is proposing an undersampled encoder in which the encoding of the data is carried out at reduced quality.
FIG. 1 is a reminder of the principle implemented in managing the energy of a mobile terminal. To increase the possibilities for making savings, the standard proposes to exchange metadata from an encoder 1 to one or more final decoders 2 (a single decoder is represented in the figure for reasons of simplification). In addition to the conventional data stream generated by the video coder, the metadata Md are multiplexed with the conventional data stream F, to obtain a data stream Fm. This data stream Fm is thereafter transmitted to a receiver 2 through a communication network, for example. The type of network used depends on the application or on the system considered. The protocol put in place is then different. Telebroadcasting, better known by the term “broadcast” or “streaming”, may be cited as an example. The insertion of the metadata then depends on the protocol or on the mode of transport. They can be inserted into additional enhancement information (or SEI, short for Supplemental Enhancement Information, message) or else be encapsulated in higher-level descriptions such as the type known by the name MPD (Media Presentation Description) for streaming applications for example of the aforementioned DASH type. The metadata emission frequency can occur at several levels, for example, at the frame level, at the Group of Pictures or GOP (17 frames for example) level. The decoder will test in the associated field in a frame the presence or otherwise of the metadatum for the sequence to be decoded. The encoder can take a decision regarding a change of metadata streaming frequency when parameters evolve such as an evolution of content (change of scene) or of type of compression (quantization parameter).
A preprocessor 101 analyses the source content Fs and a video coder 102 encodes the content of an input video. The data stream containing the coded data and the metadata is transmitted to the receiver and decoded by a video decoder 106 which transmits the decoded information to a display module 109. The metadatum Md is extracted by means of an analyzer 104 at the level of the video encoder 102 and in this case the metadatum is encapsulated in a stream in accordance with the format of the video encoder, or at the level 103 of the preprocessor 101 and the metadatum is then multiplexed with the stream. The metadatum Md is used by the final decoder 2 to reduce the power required for decoding and for presentation of the data. At the level of the final decoder 2, the video decoder 106 analyses, 107, the stream Fm containing the multimedia stream F and the metadata Md, and transmits the metadata Md to a power or energy control module 108. This energy control module will, for example, decode the metadatum or metadata Md and then apply energy consumption reduction operations for the decoding and the display of the video streams, Pc for example. The same energy control module is present at the coder level.
FIG. 2 represents a known architecture of the video encoder comprising a video decoder 20. The video input (compressed data) is transmitted to a transformation module 111 an output of which is linked with an encoding module 112 and an inverse quantization and transformation module 113. The coded multimedia data Fc are transmitted to a stream generation module 114 which will also receive motion estimation information arising from a motion estimation module 115 which receives, on the one hand the video input Ev, and on the other hand an image resulting from the application of a loop filter 116 (known to the person skilled in the art) receiving the motion compensation parameters or vectors 117 to be applied to the parameters of the image and the image parameters obtained by applying the inverse quantization inverse transform. An output of the loop filter generates a video output Sv. The stream generation module produces a compressed data stream which will be transmitted to the decoder. A buffer memory 119 allows the storage of the video images before transmission to the motion compensation module and to the motion estimation module 115.
Patent application US 2002080874 describes a system for decoding a data stream representative of a video content and deals with the capacity of decoders of varied complexity of architectures to decode an incoming stream.
In the following description, the word terminal refers, for example, to a mobile, a tablet or any connected device making it possible to receive multimedia streams. The term multimedia stream can refer to various programs, such as films, music (video clip), which are distributed through communication networks.